When performing minimally invasive percutaneous spinal surgery on a prone lying patient, such as when accessing the patient's intervertebral area for the insertion of intervertebral inserts or the performing of a discectomy, the various necessary surgical tools and/or inserts should preferably access the patient's spine in a posterolateral approach which is co-planar to the intervertebral plane passing between two selected adjacent vertebrae. Maintaining accurate positioning and guidance of surgical tools in this intervertebral plane has proven quite difficult to achieve in practice. Such positioning difficulties are further complicated by the fact that the intervertebral plane passing between any two adjacent vertebrae will be unique to that pair of adjacent vertebrae due to natural lordotic spinal curvature, sagittal plane variances as well as coronal plane variances.